The present invention is directed to centrifuge tubes and, more particularly, is directed to a permanently enclosed or sealed centrifuge tube requiring no capping means.
Typical centrifuge rotor tubes have a generally uniform cylindrical shape with one end being completely open to receive the fluid sample for subjection to centrifugation. After the introduction of the fluid sample within the tube, some type of capping means is required on the open end of the tubes when used in rotors wherein the tube is placed in a fixed position oriented at an acute angle or even zero degrees to the spin axis of the rotor. The removable capping means is necessary to prevent leakage of the fluid sample from the tube that could otherwise be caused by the large hydrostatic forces generated during high speed centrifugation.
A continual problem with the placement of capping means on the open ended centrifuge tubes is ensuring that a proper seal has been achieved between the cap and the tube to prevent any possible or potential leakage which could occur. Although swinging bucket type of rotors do not require capping means to establish a seal over the top of the centrifuge tubes because the centrifugal forces are directed toward the bottom of the bucket, sealing concerns increase as the angle orientation of the tube with respect to the spin axis is less than 90.degree.. The most significant concern for sealing the centrifuge tube occurs when the angle of the tube with respect to the spin axis is zero or essentially vertical. Various configurations have been devised for capping centrifuge tubes to eliminate any potential leakage which may occur. Present capping means are typically very complicated in their manufacture and construction as well as in their use and application for attachment to the tube.
The significance of eliminating or preventing any potential leakage in a high speed centrifuge cannot be underestimated, because the fluid sample may contain some type of bacteria or some valuable type of material which the user does not wish to lose through leakage during the centrifugation run. Further, any leakage which may occur during the centrifugation run will invalidate the run resulting in great inefficiency in the use of the centrifuge. Since many of the fluid samples which are investigated during the centrifuge run contain important ingredients for use by a scientist or technician, the leakage of a centrifuge tube during a run can create significant problems as well as the waste of an operator's time.
In many instances, the resulting leak is caused by an improper seal being achieved between the capping means and the centrifuge tube because of either a poor configuration or design of the capping means or as a result of the improper placement of the capping means on the tube. Not only is it important that the capping means be designed to achieve a secure seal between the test tube and the capping means prior to the centrifugation run, but also it is important that the capping means have such a design that it is easy to remove after the centrifugation run without having to disturb the contents of the fluid sample after the centrifugation. Otherwise, the sample constituents may be remixed and invalidate the centrifugation run.
Typically the capping means is utilized on a disposable type of centrifuge tube which is somewhat flexible. Many of the capping means used are designed to tightly grip the open end of the centrifuge tube which is flexible or pliable and conform the open end of the tube to the gripping portion of the capping means. However, the open end of the tube must be inserted properly and completely within the capping means in order to achieve a secure seal when the capping means is tightened. Unfortunately, the tube often is not completely inserted within the capping means, so that, when the cap is tightened, a proper seal is not achieved.
Present capping means utilized to achieve a proper seal not only are somewhat complicated in design and construction, resulting in a somewhat difficult and less than perfect manner in which to seal the centrifuge tube, but also are an expensive part of the centrifuge rotor and tube assembly.
A significant problem faced by users of centrifuge apparatus having tubes with present capping means is the possible contamination of the fluid sample within the tube by its contact with the material utilized to construct the capping means. In other words, the metal and plastic pieces typically utilized to construct the capping means may cause some type of contamination or reaction with the fluid sample that would invalidate the test being conducted on that particular sample.
In addition to the concern with respect to the material in the capping assembly structure contaminating the fluid sample within the tube, there is a continual concern with respect to corrosion of the cap components or members from the fluid sample in the tube after repeated use, resulting in an unusable cap or one which does not seal properly.
As stated previously, the typical centrifuge tube utilized in many rotors is made of a very pliable or flexible material, andd it is necessary that the tube be completely filled with the fluid sample in order to provide the necessary interior support to the tube during centrifugation, so that the centrifugal side of the tube does not collapse and cause the pulling of the tube out of the capping means.